The Nexus One Android 2.2 OTA Update file URL has been found and it’s already in the hands of the developers.
You can download it for yourself here: ( Google Removed it)
http://android.clients.google.com/packages/passion/signed-passion-FRF50-from-ERE27.1e519a24.zip
UPDATE: Google removed the file. You can now download it here
Give the developers a few hours and I’m sure we’ll see a rooted version.
UPDATE:
If you want to flash the downloaded update file, follow this guide: